Binary Decriptors in Feature Matching

I just wanted to learn about the feature detectors, descriptors and matchers.

I was clear with the detectors and descriptors after my research work and came to know that descriptors are used to describe the detectors found in an image. The descriptors need be rotation, orientation and scale invariant. Every descriptors has a corresponding detector but not the vice versa as every feature can't be described using a descriptor. A clear explanation on this topic is described in opencv.org documents and I have read it.

Brute Force Matcher tests every possible match. There's nothing else to say. For each point in the left image, calculate the distance to every point in the right image. It matches to the one with the shortest distance.

Unless you want to know how the cv::line function works to do the drawing, in which case I have no idea. That doesn't have anything to do with feature matching though.